JP2003246144A - Method for recording image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for recording an image of a reversible heat- sensitive recording material capable of stably repeatedly forming the image having a clear contrast many times of 1,000 times or more with high sensitivity. <P>SOLUTION: The method for recording the image comprises the steps of recording the image by a heat generated by illuminating a laser beam by using a reversible heat-sensitive recording material containing a normally colorless or pale leuco dye, a thermally discoloring dye, and reversible developer for color developing the leuco dye by heating, reheating the leuco dye to achromatize the leuco dye so that the leuco dye is achromatized by an energy of 25 to 64% of the laser beam used for color-developing of the leuco dye. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive recording material whose color tone changes reversibly by controlling thermal energy.

[0002]

2. Description of the Related Art In recent years, reversible thermosensitive recording materials have been attracting attention because they can form temporary images and can erase the images when they are no longer needed. Typical examples thereof are Japanese Patent Laid-Open No. 6-210954 and Japanese Patent Laid-Open No. 6-210954.
No. 171225, JP-A-7-68933, JP-A-7-68934 and the like, which are usually colorless or light-colored leuco dye, and this leuco dye is colored by heating, and this is reheated. A reversible thermosensitive recording material using a reversible color developing agent for decoloring is known.

However, in such a conventional reversible thermosensitive recording material, when recording and erasing of an image by heating are repeated,
In particular, when a thermal head is used, the surface is rubbed while being heated, so that the surface of the recording layer is scratched, and if it becomes severe, a uniform image cannot be recorded. On the other hand, in JP-A-6-344673 and JP-A-8-156410, a protective layer is provided on the surface of such a reversible thermosensitive recording material to reduce scratches on the surface of the recording layer when a thermal head is used. Is proposed. However, if the conventional reversible thermosensitive recording material is provided with a protective layer, it may be difficult to say that the scratch resistance is sufficient when the number of recording and erasing increases. In addition, when recording and erasing are repeated by a method in which heat and pressure are applied to the reversible thermosensitive recording layer at the same time as in a thermal head, the reversible thermosensitive recording layer is subjected to temperature and pressure to elute the reversible thermochromic composition. However, there was a problem that the layer was destroyed and the recording density was lowered.

As a method for reducing the deterioration due to such a thermal head, Japanese Patent Laid-Open Nos. 57-82088 and 64-14077 disclose resin base materials such as vinyl chloride-vinyl acetate copolymer. In a reversible heat-sensitive recording material in which an organic low-molecular substance such as a higher fatty acid is dispersed, a method of incorporating carbon black or an infrared absorbing dye and recording with a laser beam is disclosed.
According to this method, non-contact printing is possible, but since the image is a so-called cloudy type formed by light scattering,
The contrast was low and the visibility was poor.

On the other hand, in JP-A-5-8537 and JP-A-11-151856, various photothermal conversion materials using a leuco dye and a reversible developer as a reversible thermosensitive recording material are disclosed. A system for recording with a near-infrared laser beam in combination with the above has been proposed. This system certainly gives a clear image contrast,
The formation and erasing of a highly sensitive image and the repeatability of 1000 times or more, which are important problems in practical use, have not been verified. In fact, according to an additional test by the present inventors, when a metal vapor deposition film such as Cr is used as a photothermal conversion material, it is not possible to selectively give a high absorbance in accordance with the wavelength of the near infrared laser light. Therefore, the recording sensitivity is low.

Further, the layer structure described in JP-A No. 11-151856 is not sufficient in terms of recording sensitivity. The example of the publication describes a method of erasing by changing the intensity of the irradiation light of the laser recording device. In the case of printing, it is possible to print by applying energy only to an arbitrary part, but in the case of erasing, it is necessary to apply energy to a wide area to the image to be erased, so simply change the intensity of the irradiation light. The small size method requires a long erase time. Furthermore, by making the laser light intensity for printing and the laser light intensity for erasing variable, the system becomes complicated and the data processing time required for erasing the print becomes long, so the time required for erasing and printing is extremely high. There was a problem of becoming long. In the example of the publication, after the printing and the erasing are repeated 100 times, the recording surface is observed and there is no unevenness in the recording state and the erasing state. The above repeatability has not been verified or guaranteed at all. Also, 1
Irradiation energy of near infrared laser light that can be repeated 000 times or more has not been verified. In the first place, the technology for recording by converting the energy of near infrared laser light into heat using a photothermal conversion dye has been intensively studied for write-once recording materials such as CD-R, and many times. The rewriting record relies exclusively on inorganic materials. Under the present circumstances, no technical guideline is given at all for enabling the photothermal conversion dye to be repeated a large number of times, such as 1000 times or more, by a near infrared laser beam.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to obtain an image having clear contrast with high sensitivity and 1000
An object of the present invention is to provide an image recording method of a reversible thermosensitive recording material which can be repeatedly formed and erased repeatedly over a number of times.

[0008]

As a result of studies to solve these problems, the present inventors have found that the above invention can solve the above problems.

A reversible thermosensitive recording material containing a colorless or light-colored leuco dye, a photothermal conversion dye, and a reversible developer that develops the color of the leuco dye by heating and reheats it to erase the color is used, and a laser is used. In a method of recording an image by heat generated by irradiating light, 25% or more and 65% or more of energy of laser light used for coloring the leuco dye
An image recording method characterized in that the leuco dye is decolorized with the following energy.

The image recording method as described above, characterized in that the colored leuco dye is erased by heat generated by irradiating a laser beam.

2 of laser light used for coloring leuco dye
The image recording method as described above, wherein the leuco dye that has formed color is erased by irradiating a laser beam for an irradiation time of 5% or more and 65% or less.

2 of laser light used for coloring leuco dye
The image recording method described above, characterized in that the leuco dye that has formed color is erased by irradiating a laser beam having a pulse width of 5% or more and 65% or less.

The image recording method as described above, characterized in that the color is erased by irradiating the laser light at a scanning speed of 1.6 times or more and 4 times or less of the laser light used for coloring the leuco dye.

2 of racer light used for coloring leuco dye
The image recording method as described above, characterized in that the leuco dye that has been formed with the number of spots of 5% or more and 65% or less is erased.

The above-mentioned image recording method, characterized in that the leuco dye that has formed color is erased by heat generated by irradiating a laser beam having an emission region of 800 nm or more and 1200 nm or less.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, there is provided a reversible thermosensitive recording material capable of stably forming and erasing an image having a clear contrast with high sensitivity and over a large number of times of 1000 times or more. An image recording method is provided.

A reversible thermosensitive recording material which records and erases an image by repeating 1000 times or more with a near infrared laser beam using a photothermal conversion dye is required to have high heat resistance and laser light resistance. Of course, and more importantly, the recording and erasing of an image should be carried out by a method with less load on the reversible thermosensitive recording material. The present inventors diligently studied a method capable of repeatedly recording and erasing an image on the recording material without contact, and as a result, regardless of the amount of the photothermal conversion dye contained,
The leuco dye can develop color without causing ablation. By erasing by irradiating with laser light having energy of 25% or more and 65% or less of laser irradiation energy, it is possible to record / erase an image with clear contrast.
I have found that it can be repeated many times over and over. The more preferable erasing energy is 30% or more and 50% or less of the laser irradiation energy that can develop the leuco dye without causing ablation, and by using the energy in this range, 2000
We have found that images can be recorded and erased more than once.

As a method of changing the irradiation energy of the laser light used for recording and erasing, a method of changing the irradiation time of the laser light while keeping the laser output constant, a method of changing the laser output itself, and moving the laser focus. There is a method of changing the laser energy reaching the recording surface by a method, a method of applying a filter, or the like. According to the study of the present inventors, among these, a method of changing the laser energy reaching the recording surface by changing the irradiation time of the laser beam while keeping the laser output constant, recording an image many times It is preferable because erasing can be realized at a higher level. When the laser output is kept constant, by setting the laser light irradiation time during erasing within the range of 25% or more and 65% or less of the laser light irradiation time required for coloring the leuco dye, the energy applied to the unit area is set to 25 It can be set in the range of from% to 65%. High-speed erasing is possible by shortening the laser light irradiation time without reducing the laser output.

As a method of changing the laser irradiation time, there is a method of changing the laser scanning speed. When the laser output is constant, the laser light irradiation time can be set to 25% or more and 63% or less by setting 1.6 times or more and 4 times or less of the laser scanning speed required for coloring the leuco dye. .

As a method of erasing an image with a pulsed laser, the laser output and the number of spots in a unit area are kept constant, and the time (pulse width) for irradiating one spot with the laser light is changed to obtain a laser beam in a unit area. The irradiation time can be adjusted. The pulse width during erasing should be 25% or more of the pulse width required for coloring the leuco dye 65
The laser light irradiation time can be set to 25% or more and 65% or less by setting the ratio to be% or less.

Further, by keeping the laser output and the pulse width constant and reducing the number of spots of the laser light, the laser light irradiation time per unit area can be shortened. In this case, the laser light irradiation time can be set to 25% or more and 65% or less by setting the number of spots to 25% or more and 65% or less of the number of spots required for coloring the leuco dye. The number of spots can be changed by irradiating every few spots with a laser beam, irradiating every few lines with a laser beam, or by combining these spots of laser light radiated per unit area. The number of can be changed. In order to reduce unevenness when erasing an image, it is preferable to irradiate a laser beam with a regular pattern.

The method for adjusting the laser light irradiation time may be a combination of the above methods. For example, the erasing energy can be set to 25% of the laser irradiation energy during image formation by setting the pulse width during erasing to 50% during image formation and the number of spots to 50% during image formation.

In the present invention, a preferable example of the near infrared laser used for recording and erasing an image is 740n.
a semiconductor laser having a light emitting region at m to 910 nm or 90
A YAG laser having an emission region of 0 nm to 1500 nm can be used. In the case of image erasing, since the colored leuco dye is irradiated with laser light, it is more preferable to use laser light of 800 nm or more for the purpose of reducing deterioration of the leuco dye. In addition, since many dyes that are stable and can efficiently convert laser light into heat have a wavelength of 1200 nm or less,
It is more preferable to use laser light having a wavelength of 00 nm or more and 1200 nm or less.

A reversible thermosensitive recording material in which an image is recorded and erased by repeating near-infrared laser light 1000 times or more using a photothermal conversion dye is required to have high heat resistance and laser light resistance. Among the constituent materials of this recording material, the laser light resistance property of the photothermal conversion dye is the most important factor for recording and erasing many times. Specific examples of the photothermal conversion dye used in the present invention include, but are not limited to, phthalocyanine compounds, metal complex compounds, polymethine compounds, and naphthoquinone compounds. As a preferable photothermal conversion dye, photothermal conversion efficiency,
From the viewpoint of solubility in a solvent, dispersibility in a resin, and light resistance to ultraviolet light, a phthalocyanine compound and a metal complex compound are mentioned, and a phthalocyanine compound is particularly preferable.

As examples of the phthalocyanine compound, naphthalocyanine compounds, metal-free phthalocyanine compounds, iron phthalocyanine compounds, copper phthalocyanine compounds, zinc phthalocyanine compounds, nickel phthalocyanine compounds, vanadyl phthalocyanine compounds, indium phthalocyanine compounds, tin phthalocyanine compounds and the like are preferable. , And more preferably vanadyl phthalocyanine compounds, zinc phthalocyanine compounds, and tin phthalocyanine compounds. The phthalocyanine compound used in the present invention may have a substituent on the aromatic ring for the purpose of adjusting absorption wavelength, improving solubility in a solvent, improving light resistance and the like. As the substituent, an alkyl group, an alkyl ether group, an alkyl thioether group, an aryl ether group, an aryl thioether group, an amide group, an amino group, an alkyl ester group,
Examples thereof include an aryl ester group, a chlorine atom and a fluorine atom. When the aromatic ring has two or more substituents, they may be the same or different, and the substituents may be bonded to each other to form a ring.

The amount of the photothermal conversion dye used is preferably set so that the absorbance at the oscillation wavelength of the light source used is 0.2 or more. If the amount is less than this amount, the energy required to obtain sufficient heat is increased. On the other hand, the photothermal conversion dye also has some absorption in the visible region, and if the amount used is too large, the contrast is lowered. 400 nm
It is preferable to set the upper limit of the amount of the photothermal conversion dye used so that an average transmittance of 60 to 700 nm can be secured at 60% or more. Two or more kinds of photothermal conversion dyes can be mixed and used.

The photothermal conversion dye is preferably contained in at least one of the same layer and an adjacent layer with respect to the layer containing the leuco dye and the reversible developer, and it is contained in the same layer. Is more preferable for obtaining good sensitivity.

Specific examples of the leuco dye used in the present invention include the following, but the present invention is not limited thereto.

3-diethylamino-7-o-chlorophenylaminofluorane, 3-diethylamino-7-m-
Chlorophenylaminofluorane, 3-diethylamino-7-p-chlorophenylaminofluorane, 3-diethylamino-7-o-fluorophenylaminofluorane, 3-diethylamino-7-m-fluorophenylaminofluorane, 3-diethylamino- 7-p-fluorophenylaminofluorane, 3-di-n-butylamino-7-m-chlorophenylaminofluorane, 3-di-n-butylamino-7-p-chlorophenylaminofluorane, 3-di- n-butylamino-7-o-fluorophenylaminofluorane, 3-di-n-butylamino-7-m-fluorophenylaminofluorane, 3-
Di-n-butylamino-7-p-fluorophenylaminofluorane,

3-diethylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-o-chlorophenylaminofluorane, 3-
Diethylamino-6-methyl-7-m-chlorophenylaminofluorane, 3-diethylamino-6-methyl-
7-p-chlorophenylaminofluorane, 3-diethylamino-6-methyl-7-o-fluorophenylaminofluorane, 3-diethylamino-6-methyl-7-
o-Tolylaminofluorane, 3-diethylamino-6
-Methyl-7-m-tolylaminofluorane, 3-diethylamino-6-methyl-7-p-tolylaminofluorane, 3-diethylamino-6-methyl-7-o-trifluoromethylphenylaminofluorane, 3 -Diethylamino-6-methyl-7-m-trifluoromethylphenylaminofluorane, 3-diethylamino-6-methyl-7-p-acetylphenylaminofluorane, 3
-Diethylamino-6-methoxy-7-phenylaminofluorane, 3-diethylamino-6-ethoxy-7-
Phenylaminofluorane,

3-di-n-butylamino-6-methyl-
7-phenylaminofluorane, 3-di-n-butylamino-6-methyl-7-o-tolylaminofluorane,
3-di-n-butylamino-6-methyl-7-m-tolylaminofluorane, 3-di-n-butylamino-6-
Methyl-7-p-tolylaminofluorane, 3-di-n
-Butylamino-6-methyl-7-o-chlorophenylaminofluorane, 3-di-n-butylamino-6-methyl-7-m-chlorophenylaminofluorane, 3-
Di-n-butylamino-6-methyl-7-p-chlorophenylaminofluorane, 3-di-n-butylamino-
6-methyl-7-o-fluorophenylaminofluorane, 3-di-n-butylamino-6-methyl-7-m-
Fluorophenylaminofluorane, 3-di-n-butylamino-6-methyl-7-p-fluorophenylaminofluorane, 3-di-n-butylamino-6-methyl-7-o-trifluoromethylphenyl Aminofluorane, 3-di-n-butylamino-6-methyl-7-m-
Trifluoromethylphenylaminofluorane, 3-di-n-butylamino-6-methyl-7-p-trifluoromethylphenylaminofluorane, 3-di-n-butylamino-6-methoxy-7-phenylamino Fluorane, 3-di-n-butylamino-6-ethoxy-7-phenylaminofluorane,

3-di-n-pentylamino-6-methyl-7-phenylaminofluorane, 3-di-n-pentylamino-6-methyl-7-m-trifluoromethylphenylaminofluorane, 3- Pyrrolidyl-6-methyl-7-phenylaminofluorane, 3-piperidyl-6
-Methyl-7-phenylaminofluorane, 3-N-methyl-N-isopentylamino-6-methyl-7-phenylaminofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7- Phenylaminofluorane, 3-N-methyl-N-n-butylamino-6-methyl-7-phenylaminofluorane, 3-N-methyl-N-n-propylamino-6-methyl-7-phenylamino Fluorane, 3-N-ethyl-N-isopentylamino-6-methyl-7-phenylaminofluorane,
3-N-ethyl-N-isopentylamino-6-methyl-7-o-chlorophenylaminofluorane, 3-N-
Ethyl-N-p-tolylamino-6-methyl-7-phenylaminofluorane, 3-N-ethyl-N- (4-ethoxybutyl) amino-6-methyl-7-phenylaminofluorane, 3-diethylamino- 7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-phenylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-methyl Fluorane, 3-diethylamino-7- (3,4-dichloroanilino) fluorane, 3-diethylamino-7- (2
-Chloroanilino) fluoran,

3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) ) -3- (1,2-Dimethylindol-3-yl)
Phthalide, 3- (p-dimethylaminophenyl) -3-
(2-Methylindol-3-yl) phthalide, 3-
(P-Dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3-bis (1,
2-Dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,
3-bis (9-ethylcarbazol-3-yl) -5-
Dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6 -Dimethylaminophthalide,

3- (2-Ethoxy-4-aminophenyl) -3- (1-ethyl-2-methylindole-3-
Yl) -4-azaphthalide, 3- (2-ethoxy-4-)
Methylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3-
(2-Ethoxy-4-ethylaminophenyl) -3-
(1-Ethyl-2-methylindol-3-yl) -4
-Azaphthalide, 3- (2-ethoxy-4-propylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-hexylaminophenyl) ) -3- (1-Ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-dimethylaminophenyl) -3- (1-ethyl-2-methylindole-3) −
Yl) -4-azaphthalide, 3- (2-ethoxy-4-)
Diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3-
(2-Ethoxy-4-dipropylaminophenyl) -3
-(1-Ethyl-2-methylindol-3-yl)-
4-azaphthalide, 3- (2-ethoxy-4-dihexylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-
Ethoxy-4-phenylaminophenyl) -3- (1-
Ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-pyridylphenyl) -3- (1-ethyl-2-methylindol-3-
Yl) -4-azaphthalide, 3- (3-ethoxy-4-)
Diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide,

3- (2-Methyl-4-diethylaminophenyl) -3- (1-ethyl-2-methylindole-
3-yl) -4-azaphthalide, 3- (2-ethyl-4)
-Diethylaminophenyl) -3- (1-ethyl-2-
Methylindol-3-yl) -4-azaphthalide, 3
-(2-propyl-4-diethylaminophenyl) -3
-(1-Ethyl-2-methylindol-3-yl)-
4-Azaphthalide, 3- (2-butyl-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-pentyl-4-diethylaminophenyl) -3- (1-Ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-hexyl-4-diethylaminophenyl) -3- (1-ethyl-2-methylindole-3-
Yl) -4-azaphthalide, 3- (2-cyclohexyl-4-diethylaminophenyl) -3- (1-ethyl-
2-Methylindol-3-yl) -4-azaphthalide, 3- (2-cyano-4-diethylaminophenyl)
-3- (1-Ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-nitro-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) ) -4-Azaphthalide, 3- (2
-Chloro-4-diethylaminophenyl) -3- (1-
Ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-bromo-4-diethylaminophenyl) -3- (1-ethyl-2-methylindole-3
-Yl) -4-azaphthalide, 3- (2-methyl-4-)
Diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3-
(2-Ethoxy-4-diethylaminophenyl) -3-
(2-Methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-methyl-2-methylindol-3-
Yl) -4-azaphthalide, 3- (2-ethoxy-4-)
Diethylaminophenyl) -3- (1-propyl-2-
Methylindol-3-yl) -4-azaphthalide, 3
-(2-Ethoxy-4-diethylaminophenyl) -3
-(1-Butyl-2-methylindol-3-yl)-
4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-pentyl-2-methylindol-3-yl) -4-azaphthalide,

3- (2-Ethoxy-4-diethylaminophenyl) -3- (1-hexyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl)- 3- (1-heptyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-octyl-2-methylindole-3
-Yl) -4-azaphthalide, 3- (2-ethoxy-4)
-Diethylaminophenyl) -3- (1-nonyl-2-
Methylindol-3-yl) -4-azaphthalide, 3
-(2-Ethoxy-4-diethylaminophenyl) -3
-(1-Isopropyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-isobutyl-2-
Methylindol-3-yl) -4-azaphthalide, 3
-(2-Ethoxy-4-diethylaminophenyl) -3
-(1-Isopentyl-2-methylindol-3-yl) -4-azaphthalide,

3- (2-Ethoxy-4-diethylaminophenyl) -3- (1-methyl-2-ethylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl)- 3- (1-ethyl-
2-Propylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-butylindol-3-
Yl) -4-azaphthalide, 3- (2-ethoxy-4-)
Diethylaminophenyl) -3- (1-ethyl-2-pentylindol-3-yl) -4-azaphthalide, 3
-(2-Ethoxy-4-diethylaminophenyl) -3
-(1-Ethyl-2-hexylindol-3-yl)
-4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-isopropylindol-3-yl) -4-azaphthalide, 3-
(2-Ethoxy-4-diethylaminophenyl) -3-
(1-Ethyl-2-isobutylindol-3-yl)
-4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-phenylindol-3-yl) -4-azaphthalide,

4,4'-bis (dimethylaminophenyl) benzhydryl benzyl ether, N-chlorophenyl leuco auramine, N-2,4,5-trichlorophenyl leuco auramine, benzoyl leuco methylene blue, p-nitrobenzoyl leuco Methylene blue, 3
-Methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran, 3-propylspiro Examples thereof include benzopyran.

The above leuco dyes may be used either individually or in combination of two or more. In addition, toning can be performed by mixing a leuco dye that develops another hue.

The reversible developer used in the present invention is preferably a compound represented by the following general formula (1), but the present invention is not limited thereto.

[0041]

[Chemical 1]

In the compound represented by the general formula (1), X ¹ and X ² may be the same or different, and each does not contain an oxygen atom, a sulfur atom or a hydrocarbon group at both ends. -Represents a divalent group having a bond as a minimum structural unit. R ¹ represents a single bond or a divalent hydrocarbon group having 1 to 12 carbon atoms. R ² represents a divalent hydrocarbon group having 1 to 18 carbon atoms. Preferred is a divalent hydrocarbon group having 1 to 4 carbon atoms. R ³ represents a monovalent hydrocarbon group having 1 to 24 carbon atoms, preferably a hydrocarbon group having 6 to 24 carbon atoms, and more preferably a hydrocarbon group having 8 to 24 carbon atoms. Furthermore, the sum of carbon numbers of R ¹ , R ² and R ³ is 11 or more and 3
The case of 5 or less is particularly preferable. R ¹ , R ² and R ³ mainly represent an alkylene group and an alkyl group, respectively. R
^In the case of ¹ , it may contain an aromatic ring. f is 0 to 4
R ² and X ^{2 which} are repeated when f is 2 or more may be the same or different.

X ¹ and X ² in the general formula (1) include a divalent group having a minimum constitutional unit of a —CONH— bond which does not contain a hydrocarbon atom group at both ends, and specific examples thereof include Diacylamine (-CONHCO-), diacylhydrazine (-CONHNHCO-), oxalic acid diamide (-NH
COCONH-), acyl urea (-CONHCONH
-, -NHCONHCO-), semicarbazide (-NH
CONHNH-, -NHNHCONH-), acyl semicarbazide (-CONHNHCONH-, -NHCON)
HNHCO-), diacylaminomethane (-CONHC
H ₂ NHCO -), 1- acylamino-1- Ureidometan (-CONHCH ₂ NHCONH -, - NHCON
HCH ₂ NHCO-), malonamide (-NHCOCH
₂ CONH-), 3-acylcarbazic acid ester (-
Examples thereof include groups such as CONHNHCOO- and -OCONHNHCO-, but diacylhydrazine, oxalic acid diamide, and acyl semicarbazide are preferable.

Specific examples of the reversible color developer according to the present invention include the following structural formulas (1-1) to (1-1)
However, the present invention is not limited to this.

[0045]

[Chemical 2]

[0046]

[Chemical 3]

The reversible color developer according to the present invention is 1
One kind or a mixture of two or more kinds may be used, and the amount used is usually 5 to 5,000 with respect to a colorless or pale leuco dye.
It is mass%, preferably 10 to 3000 mass%.

Next, a specific method for producing the reversible thermosensitive recording material according to the present invention will be described, but the present invention is not limited thereto.

As a specific example of the method for producing the reversible thermosensitive recording material according to the present invention, a colorless or light-colored leuco dye, a reversible developer and a photothermal conversion dye are mainly contained as a main component, and these are coated on a support. Alternatively, a method of printing to form a reversible thermosensitive recording layer can be mentioned.

Usually, a colorless or pale-colored leuco dye, a reversible color developer, and a photothermal conversion dye are contained in the reversible thermosensitive recording layer after each compound is dissolved in a solvent or dispersed in a dispersion medium. A method of mixing, a method of dissolving each compound in a solvent or dispersing in a dispersion medium, mixing each compound by heating to dissolve and homogenize, and then cooling.
A layer can be formed by preparing a mixed solution by a method of dissolving it in a solvent or dispersing it in a dispersion medium, and coating or printing it on a support and then drying it.

When the photothermal conversion dye is contained in a layer different from the leuco dye and the reversible developer, the photothermal conversion dye is dispersed alone or together with a binder in a layer adjacent to the layer containing the reversible developer. It is preferable to contain

It is also possible to add a binder to the reversible thermosensitive recording layer for the purpose of improving the strength of the reversible thermosensitive recording layer. Specific examples of the binder include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic. Acid ester / methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, alkali salt of ethylene / maleic anhydride copolymer, polyvinyl acetate, polyurethane, polyacrylic ester, styrene / butadiene copolymer Polymer, acrylonitrile / butadiene copolymer,
Methyl acrylate / butadiene copolymer, ethylene / vinyl acetate copolymer, ethylene / vinyl chloride copolymer, polyvinyl chloride, ethylene / vinylidene chloride copolymer, polyvinylidene chloride, polycarbonate, polyvinyl butyral and the like can be mentioned. The role of these binders is
The purpose is to keep each material of the composition uniformly dispersed by applying heat for printing and erasing without deviation. Therefore, it is preferable to use a resin having high heat resistance as the binder resin. Recently, high value-added reversible thermosensitive recording materials such as prepaid cards and stored cards are often used, and along with this, high durability products such as heat resistance, water resistance, and adhesiveness are required. Is becoming. Curable resins are particularly preferable for such requirements.

Examples of the curable resin include a thermosetting resin, an electron beam curable resin, an ultraviolet curable resin and the like.
As the thermosetting resin, for example, phenoxy resin, polyvinyl butyral resin, cellulose acetate propionate resin and the like, which are cured by reacting a hydroxyl group and a carboxyl group with a crosslinking agent, can be mentioned. Examples of the crosslinking agent at this time include isocyanates, amines, phenols, epoxies and the like.

Monomers used for the electron beam and ultraviolet ray curable resins include monofunctional monomers represented by acrylics, bifunctional monomers, polyfunctional monomers and the like. In particular, in the case of ultraviolet crosslinking, photopolymerization initiation Agents and photopolymerization accelerators are used.

For the purpose of preventing aging of the reversible thermosensitive recording material, an antioxidant used in rubber products and the like can be added. Further, an antioxidant may be contained in the upper layer or the lower layer of the reversible thermosensitive recording layer. For the purpose of preventing the deterioration of the photothermal conversion dye due to ultraviolet rays, an antiaging agent may be contained in the layer containing the photothermal conversion dye or the upper layer of the layer containing the photothermal conversion dye. Antiaging agents include p, p'-diaminodiphenylmethane, aldol-α-naphthylamine, N, N'-diphenyl-
Examples thereof include amine compounds such as p-phenylenediamine, hydroquinone monobenzyl ether, phenol compounds such as 1,1-bis (p-hydroxyphenyl) cyclohexane, benzotriazole compounds, triazine compounds, benzophenone compounds, and benzoic acid esters. Other examples include o-phenylene thiourea, zinc salt of 2-aminobenzimidazole, nickel dibutylthiocarbamate, zinc oxide, paraffin and the like. Further, a polymer containing such a monomer having an antioxidant structure as one component of polymerization, or a polymer having a polymer main chain grafted with an antioxidant structure can also be used. It is also possible to use two or more anti-aging agents in combination.

A heat-fusible substance may be contained in the reversible thermosensitive recording layer as an additive for controlling the color developing sensitivity and the decoloring temperature of the reversible thermosensitive recording layer. 60 ° C
Those having a melting point of ~ 200 ° C are preferable, and especially 80 ° C.
Those having a melting point of ˜180 ° C. are preferred. It is also possible to use a sensitizer which is used for general thermal recording paper. For example, waxes such as N-hydroxymethylstearic acid amide, stearic acid amide, and palmitic acid amide, naphthol derivatives such as 2-benzyloxynaphthalene, biphenyl derivatives such as p-benzylbiphenyl and 4-allyloxybiphenyl, 1,2, and the like. -Polyether compounds such as -bis (3-methylphenoxy) ethane, 2,2'-bis (4-methoxyphenoxy) diethyl ether, bis (4-methoxyphenyl) ether, diphenyl carbonate, dibenzyl oxalate, bis (oxalate) Carbonic acid such as p-methylbenzyl) ester or an oxalic acid diester derivative or the like can be added in combination.

The support used in the reversible thermosensitive recording material according to the present invention includes paper, various non-woven fabrics, woven fabrics, synthetic resin films, synthetic resin laminated papers, synthetic papers, metal foils,
Glass or the like, or a composite sheet obtained by combining these may be arbitrarily used according to the purpose, and may be transparent, semitransparent, or opaque. Moreover, it is not limited to these.

In the layer structure of the reversible thermosensitive recording material according to the present invention, an intermediate layer may be provided between the reversible thermosensitive recording layer and the support. In this case, the protective layer and the intermediate layer may be composed of a plurality of layers of 2 layers or 3 layers or more. Further, in the reversible thermosensitive recording layer, a material capable of electrically, magnetically and optically recording information may be contained in another layer, a surface on which the reversible thermosensitive recording layer is provided or an opposite surface. . Further, a back coat layer may be provided on the surface opposite to the surface on which the reversible thermosensitive recording layer is provided for the purpose of preventing curling and preventing electrification.

For the reversible thermosensitive recording layer, protective layer and intermediate layer, diatomaceous earth, talc, kaolin, calcined kaolin,
Pigments such as calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, and urea-formalin resin, as well as higher fatty acid metal salts such as zinc stearate and calcium stearate, paraffin, paraffin oxide, polyethylene, Waxes such as oxidized polyethylene, stearic acid amide, and castor wax, dispersants such as sodium dioctylsulfosuccinate, surfactants, fluorescent dyes, and the like can be included.

[0060]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In addition, the number of copies in the examples is based on mass.

Example 1 [Preparation of reversible thermosensitive recording material] 3-diethylamino-6
-Methyl-7-m-trifluoromethylphenylaminofluoran (Yamada Chemical Co., Ltd., BLACK 100)
20 parts, N- [3- (p-hydroxyphenyl) propiono] -N'-n-docosanohydrazide 100 parts, polyester polyol (manufactured by Dainippon Ink and Chemicals, Inc.,
Bernock D-293-70) 50 parts, curing agent (manufactured by Nippon Polyurethane Co., Ltd., Coronate HL) 50 parts, methyl ethyl ketone 300 parts, toluene 300 parts to photothermal conversion dye (manufactured by Nippon Shokubai Co., Ltd., TX-EX-814). 1 part) was added, and the mixture was pulverized together with glass beads for 5 hours with a paint shaker to obtain a dispersion liquid. A solid content of 7 g of the above dispersion liquid on a polyethylene terephthalate (PET) sheet
A reversible thermosensitive recording material was obtained by coating so as to give m ² and drying.

[Print erasure test] The reversible thermosensitive recording material thus obtained was used with a continuous wave semiconductor laser with an oscillation wavelength of 830 nm, an output of 1 W and a spot system of 50 μm and a scanning speed of 100.
An image was formed under the irradiation condition of cm / sec, and the density of the color-developed portion was determined by Macbeth RD918. Then set the scanning speed to 200
The image was erased by irradiating the laser with the condition set to cm / sec. The density of the erased portion was determined by Macbeth RD918, and the erased portion and the erased fog were visually confirmed in the erased portion. The difference between the coloring density and the erasing density (referred to as the first contrast) was 0.65. By the same operation, coloring and erasing are repeated, and 500th and 1000th, 200th
When the contrast was calculated for the 0th time, they were 0.64, 0.61 and 0.58, respectively.

Examples 2 to 4 The scanning speed at the time of erasing the semiconductor laser was 222 cm / sec,
Repeated tests were similarly conducted at 250 cm / sec and 333 cm / sec.

Examples 5, 6 and Comparative Example 1 The scanning speed of the semiconductor laser during image formation was 118 cm /
Seconds, the scanning speed when erasing the semiconductor laser is 167c
Repeated tests were conducted in the same manner at m / sec, 183 cm / sec and 200 cm / sec.

Comparative Example 1 Scanning speed during image formation of a semiconductor laser was 118 cm /
Seconds, the scanning speed when erasing the semiconductor laser is 167c
Repeated tests were conducted in the same manner as m / sec.

Example 7 The scanning speed during image formation by the semiconductor laser was 83 cm / sec, and the scanning speed during erasing the semiconductor laser was 332 cm.
/ Sec, the same test was repeated.

Comparative Example 2 The scanning speed of the semiconductor laser during image formation was 83 cm / sec, and the scanning speed of the semiconductor laser during erasing was 400 cm.
/ Sec, the same test was repeated.

[Evaluation] Also in Examples 2 to 7 and Comparative Examples 1 and 2, repeated tests were conducted in the same manner as in Example 1 and the visual judgment of the erased part was as follows: complete erasure was ◯, unerased residue was Δ, color development by erasing energy. Was designated as x. Regarding the value of contrast, 0.6 or more is ⊚, 0.4 or more and less than 0.6 is ◯, 0.3 or more and less than 0.4 is Δ, and less than 0.3 is x. It shows in Table 1.

[0069]

[Table 1]

As is clear from the results shown in Table 1, Examples 1 to 1
No. 7 was completely erased even after the print was erased 1000 times, and a clear contrast was obtained. In Examples 1 to 4, even after the print was erased repeatedly 2000 times, the image was completely erased and a clear contrast was obtained.

Examples 8 to 14 and Comparative Examples 3 to 4 The pulse width during image formation was set to 63.5 μsec, and the ratio (%) of the pulse width during erasure to the pulse width during image formation.
Was set as shown in Table 2 and images were formed and erased by pulsed laser light. The laser output and spot diameter were tested under the same conditions as in Example 1. The results are shown in Table 2.

[0072]

[Table 2]

As is clear from the results of Table 2, the same results as those of Table 1 were obtained.

Examples 15 to 21 and Comparative Examples 5 to 6 The number of spots at the time of image formation was 400,000 / cm 2, and the ratio (%) of the number of spots at the time of erasure to the number of spots at the time of image formation is shown in Table 3. And the same operation as in Example 8. The results are shown in Table 3.

[0075]

[Table 3]

As is clear from the results in Table 3, the same results as those in Tables 1 and 2 were obtained.

Examples 22 to 28 and Comparative Examples 7 to 8 The ratio (%) of the laser output at the time of erasing to the laser output at the time of image formation was set as shown in Table 4, and the same operation as in Example 1 was performed. The results are shown in Table 4.

[0078]

[Table 4]

As is clear from the results of Table 4, Example 2
For 2 to 25, the same results as in Examples 1 to 7 were obtained.

Example 29 The photothermal conversion dye used in Example 1 (T manufactured by Nippon Shokubai Co., Ltd.)
X-EX-814) was changed to YKR-3080 (manufactured by Yamamoto Kasei Co., Ltd.), samples were prepared in the same manner, and the semiconductor laser used for recording and erasing images was changed to YAG laser. Except that the scanning speed was changed to 250 cm, the scanning speed during erasing was 4.8 times to 1.4 times the scanning speed during printing as in Examples 1 to 7 and Comparative Examples 1 and 2. As a result of repeating the test when the number of stages was changed, the same results as in Examples 1 to 7 were obtained when the color was erased at a scanning speed of 1.6 times or more and 4 times or less of the scanning speed at the time of image formation. .

[0081]

According to the present invention, there is provided an image recording method for a reversible thermosensitive recording material capable of stably and repeatedly forming an image having a clear contrast over 1000 times or more.

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Claims (7)

[Claims] 1. A reversible thermosensitive recording material containing a colorless or light-colored leuco dye, a photothermal conversion dye, and a reversible developer that develops a color by heating and reheats the leuco dye to decolor it. In the method of recording an image by heat generated by irradiating a laser beam, 25% or more of the energy of the laser beam used for coloring the leuco dye is 65% or more.
An image recording method characterized in that the leuco dye is decolored with an energy of not more than%. 2. The image recording method according to claim 1, wherein the colored leuco dye is decolored by heat generated by irradiating a laser beam. 3. The leuco dye that has been colored is decolored by irradiating the laser light for an irradiation time of 25% or more and 65% or less of the laser light used for coloring the leuco dye. Image recording method described. 4. The leuco dye that has been colored is erased by irradiating it with laser light having a pulse width of 25% or more and 65% or less of the laser light used for coloring the leuco dye. The image recording method according to any one of 1. 5. The leuco dye that has been colored at a scanning speed of 1.6 times or more and 4 times or less of the laser light used for coloring the leuco dye is decolored. Image recording method. 6. The image according to claim 1, wherein the colored leuco dye is decolored by the number of spots of 25% or more and 65% or less of the laser light used for coloring the leuco dye. Recording method. 7. The leuco dye that has formed color is decolored by heat generated by irradiating a laser beam having an emission region of 800 nm or more and 1200 nm or less.
7. The image recording method according to any one of 6 to 6.